1. Field of the Invention
The present invention relates, generally, to a process for the preparation of dimethylether (DME) from hydrocarbons, and, more particularly, to a process for the preparation of DME from hydrocarbons through a tri-reforming reaction and a gas-phase DME direct synthesis reaction over special catalysts in one step.
2. Description of the Related Art
Recently, DME, which has LPG-like physical properties and other excellent properties, is receiving attention as an aerosol propellant, a substitute material for diesel fuel, LPG, LPG-mixed fuel and an intermediate of chemical reactions.
In general, a process for the preparation of DME from hydrocarbons includes reforming hydrocarbons, serving as a reaction material, through a plurality of reaction procedures to synthesize a syngas, and then subjecting the syngas, serving as a reaction material, to methanol synthesis and methanol dehydration to obtain DME.
As such, the synthesis of the syngas is realized through the following three processes.
In a first process, a hydrocarbon (e.g., methane) and water vapor are catalytically reacted at about 800–900° C., to be converted into hydrogen and carbon monoxide. The production of hydrogen and carbon monoxide is conducted at a high temperature in the presence of a nickel catalyst through Reaction 1 below, and thus, hydrogen and carbon monoxide are produced at a molar ratio of 3:1:CH4+H2O→CO+3H2  Reaction 1The process using the above reaction, which was first introduced by BASF GmbH, Germany, in 1926, has been internationally popularized, and therefore, industrial foundations for thermodynamic research, catalysts, and reaction conditions have been based thereon. In the reforming reaction, having the goals of prevention of back reactions and inhibition of coking of a catalyst, water vapor is supplied in an amount three times greater than the reaction material, and the reaction temperature is maintained at 600–900° C.
In a second process, methane gas and oxygen are reacted at a high temperature to induce the combustion reaction. At this time, the temperature required for the reaction is maintained using the combustion heat generated.
In a third process, carbon dioxide and methane gas are reacted to produce hydrogen and carbon monoxide, which is referred to as CO2 dry reforming. Since this process is an endothermic reaction, it functions to decrease the temperature of the reactor. Hence, the reaction temperature has to be maintained using the combustion heat obtained in the second process.
The syngas thus obtained is synthesized into methanol using a methanol synthesis catalyst, after which methanol is transformed into DME as a final product using a methanol dehydration catalyst.
That is, the conventional DME production process is disadvantageous because at least two reaction procedures, including the conversion of syngas into methanol and the conversion of methanol into DME, should be conducted.
According to the conventional techniques, since the synthesis of the syngas from hydrocarbons and the synthesis of DME from the syngas each require at least two reaction procedures, a plurality of reactors must be operated. As such, a problem exists in that all of the reactions must be stopped if one reaction is stopped. In addition, expensive apparatus is required and high operating costs are incurred, due to the use of a plurality of reactors.
As well, carbon dioxide, generated in individual synthesis procedures, is released into the atmosphere, thus contributing to the greenhouse effect.